It is now clear that Shc proteins are targets of a diverse group of proteins including both receptor and non-receptor tyrosine kinases, immunoglobulin receptors, G-protein coupled receptors and cytokine receptors. Activation of these factors leads to tyrosine phosphorylation of Shc resulting in the recruitment of the Grb2-Sos complex and subsequent activation of the Ras signal transduction cascade. In addition, it has become clear that Shc proteins may also mediate signals in addition ro Ras activation. Although Shc proteins represent targets of a diverse array of signaling molecules, the importance of Shc proteins in the function of these proteins is still unclear. The objective of this proposal is to examine the function of Shc proteins in general and a specific Shc family member, ShcC, in particular. This objective will be accomplished through the following specific aims: (1) determine the role of Shc proteins in receptor tyrosine kinase function; (2) examine the role of the ShcC PTB domain in binding phospholipids and membrane localization; and (3) determine if ShcD functions in neural development and signaling. Using mutant forms of ShcC, they will examine the importance of Shc proteins in RTK-mediated transformation and activation of Ras. These mutant proteins will be tested for their effect on the biochemical pathways stimulated by various receptors, e.g. MAPK activation, as well as their effect on the biological consequences of chronic receptor activation, e.g. transformation. Recent evidence suggests that PTB domains may function as membrane localization signals. In addition, they may also play a role in the regulation of phospholipid signaling. They will determine the role of the ShcC PTB domain in membrane localization as a function of its ability to bind tyrosine phosphorylated proteins as well as phospholipids. Given the restricted expression of ShcC to tissues of neural origin, they will examine the role of ShcC in neural development and signaling. Through immunohistochemical staining of both embryonic as well as adult mouse tissues they will determine the precise temporal and spatial pattern of ShcC expression. Using primary mouse neuronal culture, they will determine the pattern of ShcC expression during neuronal differentiation. In conjunction with this approach, they will also utilize immortalized neuroblastoma cell lines to examine the biochemical function of ShcC in growth and differentiation. The studies proposed here will help to elucidate the function of Shc proteins in general and ShcC in particular. Furthermore, these experiments will begin to address the importance of ShcC in neural function. Given the diversity of signals which impinge on Shc proteins as well as the diversity of Shc proteins in general, this proposal will begin to determine the specific role of a novel Shc family member.